Note that you can see the numeric rotation angle in the Options bar. Check the Rotate All Windows option to simultaneously rotate all open documents.

When you reach your desired rotation angle, release the mouse button.

If you want to undo your rotation, click the Reset View button in the Options bar.

Choosing Edit→Undo or using the History panel to undo doesn’t revert your image to the original 0-degree rotation.

If you’re a user of a MacBook,, a Mac with a Magic Trackpad or Magic Mouse, or if you are using a Windows 7 computer with a multi-touch trackpad, you may be aware that you can use your trackpad to flick, rotate, or zoom. You may also have been annoyed when you did these things inadvertently, in which case you can disable Gestures in your Interface Preferences settings.

If you’re using Mac’s Lion OS, gestures are controlled in the Mouse or Trackpad preference panes in the Systems Prefences.